Hemolysis may artifactually increase the result. Levels in serum are normally 0.3 mmol/L higher than plasma levels due to liberation of potassium by platelets during clotting (c. 0.07 mmol/L per 100K platelets). Thus not only hemolysis but thrombocytosis can falsely elevate potassium levels, which can be circumvented by measuring plasma rather than serum potassium. Values < 1.5 or > 12 are automatically reassayed.